The P2138 code on your 2021 BMW 3 Series indicates a voltage correlation error between accelerator pedal position sensors D and E. This code affects your 3 Series' 2.0L TwinPower Turbo 4-cylinder or 3.0L TwinPower Turbo 6-cylinder engine's electronic throttle system.
Understanding P2138 on BMW 3 Series
The accelerator pedal assembly contains two position sensors (D and E) that must track proportionally as the pedal is pressed and released. Code P2138 sets when the voltage relationship between these two sensors doesn't meet expected correlation, indicating one sensor is producing incorrect values relative to the other.
Common Symptoms
- Check engine light on
- Drivetrain malfunction message
- Reduced power or limp mode
- Throttle response significantly limited
- Engine may only idle
- Cruise control disabled
- Possible EML (Engine Malfunction Light)
Primary Causes
- Failing accelerator pedal module
- One APP sensor drifting out of calibration
- Corroded or damaged pedal connector
- Wiring damage in pedal circuit
- 5-volt reference supply issue
- Ground circuit problem
- DME (engine control module) input fault
Diagnostic Procedure for 2021 BMW 3 Series
Using BMW-specific diagnostic software (ISTA or equivalent), monitor both APP sensor D and E voltages simultaneously. Both should change proportionally through full pedal travel. Identify which sensor is producing incorrect values. Inspect pedal connector under the dash for corrosion or damage. Test 5-volt reference and ground circuits at the pedal connector. Check wiring for damage between pedal and DME.
Repair Solutions
If APP sensor correlation fails consistently and wiring tests good, the accelerator pedal assembly requires replacement. Use BMW-approved parts to ensure proper calibration. Repair any damaged wiring or corroded connectors found. After replacement, clear fault memory and test correlation during road test. BMW systems may require coding or registration of the new pedal assembly.